How to use
- Type your A1C result, for example 6.5, into the A1C box. Your estimated average blood sugar appears at once in mg/dL and mmol/L.
- To go the other way, choose Blood sugar → A1C and type your average reading from a meter or continuous glucose monitor, in mg/dL or mmol/L.
- Read the label under the result: normal, prediabetes range or diabetes range, using the ADA and CDC cutoffs.
- Use the chart below the calculator to see how A1C and average blood sugar line up from 5% to 12%. The row closest to your result is highlighted.
What A1C measures
The A1C test (also called hemoglobin A1C or HbA1c) shows the percentage of hemoglobin in your red blood cells that has sugar attached to it. Red blood cells live about three months, so A1C reflects your average blood sugar over the past two to three months, not a single moment.
Because one finger-stick or meter reading changes from hour to hour, doctors use A1C to diagnose prediabetes and type 2 diabetes and to check how well a treatment plan is working.
How A1C converts to average blood sugar
The conversion comes from the A1C-Derived Average Glucose (ADAG) study, which compared A1C with continuous glucose readings in more than 500 people. The American Diabetes Association uses its formula: estimated average glucose (eAG) in mg/dL = 28.7 × A1C − 46.7. To get mmol/L, divide by 18.
Example: an A1C of 7% gives 28.7 × 7 − 46.7 = 154 mg/dL (8.6 mmol/L). The result is an average; your own readings will go above and below it.
A1C chart
Estimated average glucose for common A1C results, from the ADA formula.
| A1C | eAG (mg/dL) | eAG (mmol/L) |
|---|---|---|
| 5% | 97 | 5.4 |
| 5.5% | 111 | 6.2 |
| 6% | 126 | 7.0 |
| 6.5% | 140 | 7.8 |
| 7% | 154 | 8.6 |
| 7.5% | 169 | 9.4 |
| 8% | 183 | 10.2 |
| 9% | 212 | 11.8 |
| 10% | 240 | 13.4 |
| 11% | 269 | 14.9 |
| 12% | 298 | 16.5 |
Normal A1C levels
For adults, the ADA and CDC use these ranges for diagnosis: below 5.7% is normal, 5.7% to 6.4% is prediabetes, and 6.5% or higher on two separate tests indicates diabetes.
For many adults who already have diabetes, the ADA suggests an A1C goal below 7%, but your doctor may set a higher or lower target based on your age, other conditions and risk of low blood sugar.
| A1C | Meaning | Average blood sugar |
|---|---|---|
| Below 5.7% | Normal | Below about 117 mg/dL (6.5 mmol/L) |
| 5.7% to 6.4% | Prediabetes | About 117 to 137 mg/dL (6.5 to 7.6 mmol/L) |
| 6.5% or higher | Diabetes | About 140 mg/dL (7.8 mmol/L) or higher |
Frequently asked questions
Why doesn't my meter average match my A1C?
A meter only counts the moments you test, often before meals, while A1C covers every hour of the day and night. Anemia, recent blood loss or transfusion, kidney disease, pregnancy and some hemoglobin variants can also make A1C read higher or lower than your true average.
Can I use this to diagnose diabetes?
No. Diagnosis needs a lab A1C or other blood test, usually repeated, and a doctor's review. This calculator only converts numbers so you can understand a result you already have.
What is IFCC A1C in mmol/mol?
The UK, Europe and Australia report A1C in mmol/mol (IFCC units) instead of percent. The calculator shows both; for example, 6.5% equals 48 mmol/mol and 7% equals 53 mmol/mol.
How quickly can A1C change?
Because it reflects about three months, A1C changes slowly. Doctors usually recheck it every three months while treatment is being adjusted, and every six months once it is stable.
Is my result saved or sent anywhere?
No. The conversion runs in your browser and nothing you type leaves your device.
